1. Field of the Invention
The present invention relates to a laminated heat exchanger which can be used in a vehicle air conditioning system and in particular, a laminated heat exchanger that is provided with a pair of tanks formed on one side and with both intake and outlet portions provided parallel to each other in one of the end plates.
2. Description of the Related Art
Laminated heat exchangers of this type, that have been developed by the Applicant of the present invention, have a structure in which the core of the laminated heat exchanger is formed by laminating a plurality of levels of tube elements. A pipe passage is formed between one group of tanks and another group of tanks in a tube element group. A communicating pipe is provided in the pipe passage with one end of the communicating pipe connected to a tank in the tank group and the other end of the communicating pipe connected to a coolant passage which is formed outside of the end plate.
One end of the communicating pipe is inserted in the opening of the tank and the other end is inserted in the opening of the end plate in advance before assembling the communicating pipe in the core of the laminated heat exchanger and before brazing in the furnace, in order to prevent any misalignment between the connecting pipe and the opening of the tank or a misalignment between the communicating pipe and the opening of the end plate. The communicating pipe is then mounted in the laminated heat exchanger by securing the entire laminated heat exchanger with jigs or the like and then brazing it in the furnace.
However, in the structure described above, when brazing the laminated heat exchanger in the furnace, the length of the laminated heat exchanger in the direction of lamination is reduced by approximately 3 mm-6 mm, as the solder on the surface of the tube elements melts. This may cause one end of the communicating pipe to extend too far into the distribution tank and, at the same time, cause the other end to extend too far into the coolant passage formed outside of the end plate.
We can assume that this will greatly reduce the opening area of the communicating pipe and consequently increase resistance to flow of the coolant into the communicating pipe from an intake/outlet pipe via the coolant passage or flow of the coolant into any tank from the communicating pipe.